The present invention generally relates to communication protocols and more particularly to a communication protocol for transferring messaging information between a messaging server and a remote device over a communication network using an acoustically coupled modem.
Letters were once, and in some places still are, the sole method of long distant personal and business communication. Communication progressed through the telegraph period. The advent and proliferation of the telephone caused the telephone call to rival the letter as the preferred method of personal and business communication.
The Internet and widespread use of Personal Computers, led to electronic messaging, using a modem, as a popular method of communication for both personal and business uses. In effect, the letter and the telephone were combined. The Personal Computer produced the electronic message, i.e., letter, and this was transferred to the telephone network via a modem. Modems, which once were external and acoustical, are now embedded in Personal Computers, laptops, or Personal Digital Assistants.
However, these modems typically need a telephone jack, are slow in establishing a connection to an electronic messaging server, and are frequently error prone in transferring data. One problem with today's modem technology is that most public access telephones do not have an external jack. Thus, a business traveler at an airport would have to search for an external jack, even though many public telephones may be available.
Conventional acoustically coupled modems attempted to solve this problem by providing an easy connection to a telephone handset wherein a connection to RJ-4 or RJ-11 jack was not required. These modems were external devices connected to the Personal Computer with an telephone cradle to hold a telephone headset. A typical modem would have muffs over the earpiece and the mouthpiece of the telephone handset to filter out external noise. This interface between the telephone handset and the modem had several disadvantages including: 1) the modem was bulky, and 2) despite the mechanical damping, it was susceptible to noise; hence data transfer was error prone. Little or no error correction was used. These problems led to the conventional acoustically coupled modem losing popularity in the market.
There are several other problems associated with conventional acoustically coupled computer modems. The connection phase of modem operation includes an extensive hand-shaking procedure. The error detection and retransmission mechanisms used during the data exchange phase are inadequate and error prone. The net effect is to prolong the time on the telephone and delay the sending and receiving of electronic messages between remote device and messaging server.
Therefore in the blossoming market of electronic messaging, there is a need for a remote device which can communicate with a remote messaging sever via a telephone network in an expedited and error-free manner. A portable, hand-held acoustically coupled modem is needed, that can be easily connected to any telephone. The acoustically coupled modem should provide a fast and reliable connection procedure, and perform fast, robust, and error free data transfer. A goal should be the minimization of total time on the telephone needed for connection, data transfer, and disconnection.